A. Field of Invention
The present invention relates to the art of slurry pumping devices and more specifically to progressive cavity pumps and pumping systems.
B. Description of the Related Art
Currently in the art progressive cavity pumps are known to dispense a slurry or aggregate material, such as cement, stucco or synthetic coatings. The aggregate material is received through a material inlet and is metered through the barrel of the pump by the rotating action of an internal rotor. The rotor builds pressure at the dispensing end where the aggregate material is then ejected under pressure through a spray gun. When the pump is shut off or idled pressure is trapped in the barrel and in a hose connecting the barrel to the spray gun. Under pressure, the aggregate material is subjected to xe2x80x9cdry packingxe2x80x9d wherein the more viscous material of the slurry is separated from the aggregate leaving drier and more condensed material in the barrel. This can lead to increase wear of the pump components, including the pump barrel and the rotor, especially during start up. What is needed is a pump that reduces the pressure in the barrel, the hose and the spray gun, after shut down or idling of the pump, thus preventing separation of the aggregate material.
It is an object of the present invention to provide a method for starting up a pumping system wherein a rotor member is automatically driven in second direction for a selectively adjusted amount of time prior to driving the rotor member in a first direction, wherein the driving the rotor member in a first direction causes a dispensing of an associated aggregate material.
It is another object of the present invention to provide a method for shutting down a pumping system wherein a rotor member is automatically driven in second direction for a selectively adjusted amount of time after initiating shutdown or idling of the pumping system from being driven in a first direction.
It is even another object of the present invention to provide a pumping system, and more specifically a slurry pumping system that automatically reduces the pressure in the pump housing by reversing the rotor member contained therein for a predetermined amount of time during shutdown of idling of the pumping system.
It is another object of the present invention to provide a pumping system, and more specifically a slurry pumping system that automatically reverses the direction of the rotor member for a predetermined amount of time during start up of the pumping system.
It is yet another object of the present invention to provide a prime mover that drives the rotor member in first and second directions.
It is still another object of the present invention to provide a controlling means that actuates the prime mover.
It is still yet another object of the present invention to provide a controlling means that automatically causes the rotor member to be driven in a second direction after initiating shutdown of the pumping system and prior to start up of the pumping system.
In accordance with the present invention, there is provided a pumping system that includes a pump housing and a rotor member received within the pump housing, wherein the rotor member is driven in a first direction to dispense an associated aggregate material. The pumping system further comprises a prime mover operatively coupled to the rotor member for use in driving the rotor member in first and second directions. The prime mover is operatively communicated to and driven by a controlling means that automatically drives the rotor member the second direction after shut off or idling of the pumping system is initiated. The controlling means also automatically drives the prime mover, and consequently the rotor member in the second direction for a predetermined amount of time when the shutting down of the pumping system is initiated. The time period for driving the rotor member in the second direction is selectively determined by a first potentiometer operatively communicated to the controlling means and adjusted by the operated to the desired length of time. During shut down of the pumping system, while the pumping system is operating, the operator adjusts the first potentiometer, then initiates shutdown of the pumping system, after which the controlling means automatically reverses the direction that the rotor member is driven for the predetermined period of time set by the first potentiometer. In this way the pressure in the dispensing end or second of the pump housing is reduced preventing or reducing the affects of material separation due to dry packing.
Other objects and advantages of the invention will appear from the following detailed description of the preferred embodiment of the invention with reference being made to the accompanying drawings.